1. Field of the Invention
The present invention relates to a display device, especially a brightness control device can unify the brightness of the display device that and a method thereof.
2. Description of the Related Art
Structurally, a size of a fluorescent substance at the corner of a cathode ray tube is smaller than a size of a fluorescent substance at the center portion of the cathode ray tube. A thickness for the corner is thicker than a thickness of the center portion of the cathode ray tube. The ratio of a transmitted light of the corner of the cathode ray tube is lower than the center portion of the cathode ray tube. Thus, the corner portion of the cathode ray tube is darker than the center portion of the cathode ray tube. The declination of the brightness between the center and the corner is between 20%.about.30%.